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// Support for atomic operations -*- C++ -*-

// Copyright (C) 2004, 2005, 2006, 2008, 2009 Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the

// terms of the GNU General Public License as published by the

// Free Software Foundation; either version 3, or (at your option)

// any later version.

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

/** @file atomicity.h

 *  This is an internal header file, included by other library headers.

 *  You should not attempt to use it directly.

 */

#ifndef _GLIBCXX_ATOMICITY_H

#define _GLIBCXX_ATOMICITY_H    1

#include <bits/c++config.h>

#include <bits/gthr.h>

#include <bits/atomic_word.h>

_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)

  // Functions for portable atomic access.

  // To abstract locking primitives across all thread policies, use:

  // __exchange_and_add_dispatch

  // __atomic_add_dispatch

#ifdef _GLIBCXX_ATOMIC_BUILTINS_4

  static inline _Atomic_word

  __exchange_and_add(volatile _Atomic_word* __mem, int __val)

  { return __sync_fetch_and_add(__mem, __val); }

  static inline void

  __atomic_add(volatile _Atomic_word* __mem, int __val)

  { __sync_fetch_and_add(__mem, __val); }

#else

  _Atomic_word

  __attribute__ ((__unused__))

  __exchange_and_add(volatile _Atomic_word*, int) throw ();

  void

  __attribute__ ((__unused__))

  __atomic_add(volatile _Atomic_word*, int) throw ();

#endif

  static inline _Atomic_word

  __exchange_and_add_single(_Atomic_word* __mem, int __val)

  {

    _Atomic_word __result = *__mem;

    *__mem += __val;

    return __result;

  }

  static inline void

  __atomic_add_single(_Atomic_word* __mem, int __val)

  { *__mem += __val; }

  static inline _Atomic_word

  __attribute__ ((__unused__))

  __exchange_and_add_dispatch(_Atomic_word* __mem, int __val)

  {

#ifdef __GTHREADS

    if (__gthread_active_p())

      return __exchange_and_add(__mem, __val);

    else

      return __exchange_and_add_single(__mem, __val);

#else

    return __exchange_and_add_single(__mem, __val);

#endif

  }

  static inline void

  __attribute__ ((__unused__))

  __atomic_add_dispatch(_Atomic_word* __mem, int __val)

  {

#ifdef __GTHREADS

    if (__gthread_active_p())

      __atomic_add(__mem, __val);

    else

      __atomic_add_single(__mem, __val);

#else

    __atomic_add_single(__mem, __val);

#endif

  }

_GLIBCXX_END_NAMESPACE

// Even if the CPU doesn't need a memory barrier, we need to ensure

// that the compiler doesn't reorder memory accesses across the

// barriers.

#ifndef _GLIBCXX_READ_MEM_BARRIER

#define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("":::"memory")

#endif

#ifndef _GLIBCXX_WRITE_MEM_BARRIER

#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("":::"memory")

#endif

#endif